Highly accurate estimation of the inclination angle of a traveling object during travel (specifically, the central angle of rolling in a predetermined cross-section surface of a traveling object) is advantageous in the operation of the traveling object. Container cargo vehicle, which is an example of the traveling object, is used for transportation of container cargos imported and exported in the international commercial trading, and the inclination angle of the container cargo vehicle during travel, in a cross-section surface perpendicular to the travel direction of the container cargo vehicle, provides valuable data that directly reflects the biased loading of the cargos in the container. Thus, accurate estimation of the inclination angle is advantageous to prediction of possible collapse/falling of cargo piles that can take place when the door of the container is opened and unstable traveling of the vehicle on, for example, a curved road or due to malfunction of suspensions.
In this specification, the “biased loading” of the cargos in the container means the deviation of a load point determined by the center of gravity of the container cargo in a space depending on the disposition of the container cargo, and it does not mean the deviation of a load point on the plane bottom surface of the container as generally understood in container transportation business. (The “biased loading” in this specification is also referred to as “one-side loading” because of loaded state of cargos.)
Conventional technology of the inclination angle (inclination angle of road surface or inclination angle with respect to a horizontal surface) of a traveling object (movable object) during travel is disclosed in, for example, Patent Literatures 1 and 2.
In Patent Literature 1, correction is made for the inclination angle that is an angle with respect to a horizontal surface and is obtained by a rotation angle detector on the basis of the acceleration in the front/rear direction and left/right direction of a traveling object during travel.
In Patent Literature 2, a traveling object is determined to be in a stop state or in a traveling state with a constant speed when detection data series of an acceleration sensor is random, and the inclination angle of a road surface is calculated based on an output value of an acceleration.